Preservation of ether



May 19, 1953 E. MALLINCKRODT, JR., ET AL PRESERVATION OF ETHER Original Filed Feb. 12, 1949 FIGZ.

Patented May 19, 1953 2,639,243 PRESERVATION F ETHER- Edward Mallinckrodt, Jr., St. Louis, and Archie E. Ruehle, Kirkwood, Mo., assignors to Mallinckrodt Chemical Works, St. Louis, Mo., a corporation of Missouri Original application February 12, 1949, Serial No. 76,142. Divided and this application February 5, 1951, Serial No. 209,396

(o1. 14s s) 7 Claims.

This invention relates to the preservation of ether and more particularly to methods of manufacturing ether containers.

This application is a division of our copending application Serial No. 76,142 filed February 12, 1949, now Patent 2,587,744.

' Briefly this invention relates to methods for manufacturing ether containers by applying to an internal surface of a container which has a layer of tin on the interior thereof, a thermally unstable copper compound and thereafter baking the container to form a mixture of cupric oxide and tin oxide on an internal surface thereof. I

Among the objects of the present invention are the provision of improved means for protecting packaged ether against decomposition; the provision of means of the character described which do not cause corrosion of the container; and, the provision of a process for manufacturing improved ether containers. Other features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the steps and sequence of steps, and features of manipulation, which will be exemplified in the methods hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which one of various possible embodiments of the invention is illustrated, v

Fig. 1 is a vertical section through an ether can made by the processes of the present invention; and,

Fig. 2 is a section taken along the line 22 on Fig. l but on an enlarged scale.

Similar reference characters indicate corresponding parts throughout the several views of the drawing.

Because diethyl ether is a highly volatile and inflammable liquid which is hazardous to ship and store, it is usually packaged in containers made of tin plate in preference to containers made of glass or other fragile materials. From the standpoint of safety, durability, and low cost, tin cans have been entirely satisfactory as containers for ether and their use has been widespread for many years. They are, however, subject to one serious disadvantage. Conventional bright tin-plate greatly increases the tendency for ether to be oxidized by air in the container. Aldehydes and peroxides which may be formed by such oxidation are particularly ob- 2 jectionable in anesthetic ether, as evidenced by their limitation to merest traces by the U. S. Pharmacopoeia.

It has been customary to overcome this disadvantage to a considerable extent by covering the inner surface of the container with either an adherent layer of tin oxide or with a coatin of metallic copper. The adherent layer of tin oxide is usually produced by heating the cans at an elevated temperature. The treatment is simple, but it has been found that the protection which it affords the ether is somewhat variable. Copper plating the can, on the other hand, is more complicated and also has the disadvantage that it is difficult to apply a copper coatin to the tin surface without increasing the tendency of the container to corrode. Other methods have also been proposed, for example, to package the ether in contact with reducing substances, such as cuprous oxide or iron, but these methods have found little favor.

In accordance with the present invention there is manufactured an improved ether container comprising a can made of conventional tinplate, especially treated to produce an adherent coating of cupric and tin oxides on the inner surface. Containers of this type have been found to possess definite advantages. The coating is easily and inexpensively applied by the methods of the present invention using simple, readily available equipment, and provides reliable protection. It is visible on the surface of the tin as a semi-transparent brown stain which is practically insoluble in ether and is not dislodged by agitation of ether in the container.

Referring now to the drawing, an ether can I having conventional side walls 3, bottom 5 and top 7 is shown. An opening 9 in top I receives neck H which is of a type to receive a vapor-tight closure member H3.

The interior of container i is coated as shown at [5 (see Fig. 2) with an adherent coating of cupric and tin oxides. The relative thickness of the coating has been exaggerated in the drawing to show its location.

The protective coating is preferably produced by wetting the interior of the container with a solution of a thermally unstable copper compound, then drying the surface of the container by directing a stream of warm air against it, and finally heating the container in the presence of air at a temperature and for a time sufl'icient to convert substantially all of the copper to a divalent oxide and simultaneously to form a surface layer of tin oxide. Part or all of these oxides may be in the form of a double oxide of copper and tin, but for the purposes of this invention the exact composition need not be known. What isv important is that the oxide layer is adherent and affords reliable protection to the ether.

Examples of thermally unstable copper compounds of the type which can be used with this invention are copper acetate, copper formate, and copper acetylacetonate. Numerou solvents for the preferred copper compounds are known, but the adherence of the oxide coating formed by the processes of this invention is to a large degree dependent upon the nature of the solvent employed. We have found that the use of amines or mixtures of amines as solvents lead to the most strongly adherent coating. For reasons of economy we prefer to dilute the amine solutions of the copper salts with a low cost solvent, for example, isopropyl alcohol. A mixtur of equal parts by volume of diethylamine and di-isopropylamine is particularly desirable as this mixture evaporates at substantially the same rate as isopropyl alcohol. The concentration of the copper salts in the solution need be only a few tenths of a per cent for maximum protection. Th exact percentage is not critical, but no advantage isv derived from using a greater percentage and there is the danger that as the oxide coating becomes thicker it may also become weaker and break away from the surface of the can, thereby producing a residue in the ether. Many solvents may be used as diluents for the amine solution in place of isopropyl alcohol. Among them are. ether, the lower aliphatic alcohols, ethyl acetate, petroleum ether, and toluene.

Example A number of tin cans, of the type commonly employed for packaging ether, were treated in the following manner. A stock solution was prepared by dissolving 15 pounds of cupric acetate in a mixture of gallons of di-isopropylamine and 10 gallons of diethylamine. To 1 gallon of this solution, sufficient isopropyl alcohol was added to make. a total volume of 38 gallons. Some of the resulting solution was poured into each of the cans to be treated, the cans were turned and rotated so that the inner surface was entirely wetted with the solution, and the excess solution was then poured out. The cans were dried with a stream of hot air, then baked at a temperature of about 155-160 C. for 36 hours. The containers were filled with anesthetic grade ether, sealed in the customary manner, and then stored at a temperature of 90 F. Periodically, cans were selected at random and the contents were tested for the presence of aldehydes and peroxides.

After thirteen months the ether met all the requirements of the tests of the U. S. Pharmacopoeia. Moreover, when tested by still more sensitive methods no trace of aldehydes or peroxides was found. In control. experiments conducted in parallel, ether stored in untreated but otherwise identical containers failed badly in the limiting tests of the U. S. Pharmacopoeia for aldehydes and peroxides within three months, and ether stored in containers which had been given a coating of tin oxide only showed traces of aldehydes within six months and failed to meet the minimum U. S. P. requirements within thirteen months.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above methods without departing from th scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

We claim:

1.. The method of making a container for ether Which comprises coating an internal surface of a container which has a layer of tin on the interior thereof, with a thermally unstable copper salt of an organic acid compound which decomposes upon baking in the presence of oxygen to give cupric oxide, and baking the container to form a mixture of cupric oxide and tin oxide on an internal surface thereof.

2. The method of making a container for other which comprises coating the internal surface of a container which has a layer of tin on the interior thereof, with a thermally unstable copper salt of an organic acid compound which decomposes upon baking in the presence of oxygen to give cupric oxide and which is dissolved in a solvent containing an amine, removing the solvent, and baking the container to form a mixture of cupric oxide and tin oxide on internal surfaces thereof.

3. The method of making a container for ether which comprises coating the internal surface of a container which has a layer of tin on the interior thereof, with a thermally unstable copper salt of an organic acid compound which decomposes upon baking in the presence of oxygen to give cupric oxide and which is dissolved in an amine solvent, removing the solvent, and baking the container to form a mixture of cupric oxide and tin oxide on internal surfaces thereof.

4. The method of making a container for ether which comprises coating the internal surface of a container which has a layer of tin on the interior thereof, with a thermally unstable copper salt of an organic acid compound which decomposes upon baking in the presence of oxygen to give cupric oxide and which is dissolved in an amine solvent, removing the solvent, and baking the container at a temperature of approximately fill- C. to form a mixture of cupric oxide and tin oxide on internal surfaces thereof.

5. The method of making a container for ether which comprises coating the internal surface of a container which has a layer of tin on the interior thereof, with a thermally unstable copper compound selected from the group consisting of copper acetate, copper formate and copper acetylacetonate dissolved in a solvent containing an amine, removing the solvent, and baking the container to form a mixture of cupric oxide and tin oxide on internal surfaces thereof.

6 The method of making a container for other which comprises coating internal surfaces of a container Which has a layer of tin on the interior thereof, with a thermally unstable copper compound selected from the group consisting of copper acetate, copper formate and copper acetylacetonate dissolved in a solvent containing an amine and a substance selected from the group consisting of isopropyl alcohol, ether, the lower aliphatic alcohols, ethyl acetate, petroleum ether and toluene, removing the solvent, and baking the container to form a mixture of cupric oxide and tin oxidev on the internal surface thereof.

'7. The method of making a container for ether which comprises coating th interior of a container having a layer of tin on the internal surface thereof, with a solution of cupric acetate in a mixture of di-isopropylamine, diethylamine and isopropyl alcohol, removing the solvent, and baking the container at a temperature of approximately l55-160 C.

EDWARD MALLINCKRODT, JR. ARCHIE E. RUEHLE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Nitardy June 14, 1927 Mallinckrodt et a1. Jan. 1, 1929 Lawton et al Feb. 21, 1939 Fink et al. May 2, 1939 Nelson et a1 Jan. 17, 1941 

1. THE METHOD OF MAKING A CONTAINER FOR ETHER WHICH COMPRISES COATING AN INTERNAL SURFACE OF A CONTAINER WHICH HAS A LAYER OF TIN ON THE INTERIOR THEREOF, WITH A THERMALLY UNSTABLE COPPER SALT OF AN ORGANIC ACID COMPOUND WHICH DECOMPOSES UPON BAKING IN THE PRESENCE OF OXYGEN TO GIVE CUPRIC OXIDE, AND BAKING THE CONTAINER TO FORM A MIXTURE OF CUPRIC OXIDE AND TIN OXIDE ON AN INTERNAL SURFACE THEREOF. 